Fuel and air

P0240 — Boost Pressure Sensor B Circuit Range/Performance

Severity: medium Drive with care, to a shop

What P0240 means

The engine control module compares the boost sensor B signal with the pressure expected for the current rpm, load and throttle position, and with other sensors such as MAP and barometric pressure. If the signal is out of range or doesn't agree, P0240 is stored. The cause can be the sensor, its circuit, or a real boost system problem.

Symptoms

  • Check Engine light on
  • Reduced power and sluggish acceleration
  • Limp mode
  • Higher fuel consumption
  • Hesitation or surging under load
  • Unusual turbo whistle or noise

Possible causes

  1. Failed boost pressure sensor B
  2. Open, short or corroded wiring or connector at the sensor
  3. Boost or intake leaks: hoses, clamps, intercooler
  4. Cracked or disconnected vacuum lines
  5. Turbocharger or boost control actuator (wastegate) fault
  6. Faulty MAP sensor affecting signal comparison
  7. Rarely, ECM fault or calibration issue

How to diagnose

  1. Scan all codes and freeze frame data, and note any other boost or MAP codes
  2. Inspect the sensor, connector and harness for oil, moisture, corrosion or damaged insulation
  3. Check intake pipes, clamps, intercooler and vacuum hoses for cracks and leaks
  4. Compare commanded and actual boost in live data at idle and under load
  5. Compare boost sensor B with MAP and barometric readings with the engine off
  6. Test the sensor's 5 V reference, ground and signal wire with a multimeter
  7. Check actuator movement through its full range and its vacuum line for leaks
  8. Check turbo shaft play and condition if the sensor data looks normal

Common fixes

  • Replace boost pressure sensor B
  • Repair or replace damaged wiring and connectors
  • Fix boost and vacuum leaks, replace hoses and clamps
  • Repair or replace the turbocharger or its actuator
  • Update software or replace the ECM (last resort)

Questions and answers

What does P0240 mean?

The ECM found that the boost pressure sensor B signal is out of range or doesn't match other data. The cause may be the sensor, wiring or the boost system itself.

Can I drive with P0240?

Briefly, yes, but power is probably limited. Driving long with incorrect boost can damage the engine or turbo.

Will replacing the sensor fix it?

Not always. Check the wiring, connector, hoses and any boost leaks first, or the code may come back.

This is general information about the code. The meaning can differ between makes and models: a scan tool and the repair manual for your car will show the exact cause.